Determination of the total milk-clotting activity and the percentage of chymosin activity in bovine rennets

摘要

The method is designed for carrying out a rapid analysis (in a single determination cycle) of the total activity and the percentage of chymosin activity in the test rennets relative to the reference rennets. A method of turbidimetry was used (X=450 nm). The determination of kinetic parameters of the interaction between milk and rennet solutions was performed in conditions excluding the flocculation and providing the maintenance of micellar casein structure. A parameter being registered was the time of attaining the maximum rate of an increase in the optical density of a reaction mixture. The determination of the enzymatic composition is based on the difference in changes of activities of chymosin and pepsin when changing pH of the reaction medium. The duration of the automatic determination-calculation procedure is 10 min on the average per test rennet. Reproducibility of the method is ±5% (relative value) for the total milk-clotting activity and ± (1-5) % (absolute value) for the percentage of chymosin activity by determination in the range from 98 up to 5%. It is characterized by simplicity, a small number of routine operations, an ordinary set of reagents, a low consumption of the substrate (milk), the operativeness and the objectivity of analysis.